DIY waxless base

[GeezerSteve]

This thread follows that other thread, in which DIY waxless bases were discussed among other things.

Skis: Trab Stelvio Light XL, 185cm, bases beat up from 40+ days of spring touring, rock bashes, etc. Camber like new, i.e., moderately stiff traditional alpine flex.

DIY waxless base: 30cm long, steps milled with 1" indexable end mill like this one

Background: Over the past two seasons, I have experimented with several waxless patterns on old skis, including, e.g., an arced step cut like the old rare Fischer Europa 99 Radial from the 1970s. The one pictured below seems to have the least adverse affect on downhill skiing.

Design intent: I wanted a short waxless pattern on a traditional alpine camber ski to assist travel on flats and very low angle uphills and using skins as usual.

Test results: 5 days total (1 lift assisted on test skis; 4 touring days on these Trabs in spring corn). Good things: Grip is effective on spring corn and schmoo on flats and very low angle climbs; minimal effect on downhill performance in spring conditions; unexpected benefit of reducing suction in sucky spring snow. Bad thing: a bit funky when side slipping, but I got used to it, i.e., not a problem after the first tour. Unknown: performance in mid-winter snow. Overall: successful, plan to do it to another pair of beat up touring skis.

[coldfeet]

Cool. How deep did you make the cuts, and how long is the waxless zone?

I experimented with making a waxless pattern for different reasons - not big tours, because I suck and the snow around here is not good. I wanted to turn old alpine skis into a beefy XC or XCD ski that could deal with slush, ice and whatever, and that I wouldn't mind walking over rocks.

I don't have a mill or similar, so experimented with the method of heating a cheese grater and pressing it into the ski base. This worked well, too well, on a black extruded base - it melts quickly and you can get a rough positive/negative pattern. I had to sand it down, and still it climbs great but can be a little sticky when sliding. Needs refinement.

I tried the cheese-grater method on a sintered, white base on some ancient Rossignols, and made almost no impression. I expected the sintered base to be harder, but am still amazed that I couldn't melt a dent into it with a hot piece of metal.

[JRainey]

Nice work

[GeezerSteve]

coldfeet, as noted above, the waxless pattern is c. 30cm (12") long. I intended a short pattern, enough to scoot around on the flats and very low angle uphills, but not materially affecting downhill performance. I achieved that.* The grip is nowhere near that of the Viole Vector BC or Madshus Annum, both of which are soft and have a long positive pattern, but, of course, the glide is much better (indistinguishable from the Trabs before the mod on spring snow). Note that I have been Nordic skiing for 30+ years, and have developed decent technique with a short pattern and just enough kick -- although I'll acknowledge that I don't wax my classic XC skis as cold as some really good racers.

I centered the waxless pattern under the ball of foot. The apex of the camber is at ball of foot, which is where it belongs. (Trab construction is excellent.)

*The proof of the pudding is in the eating. Last weekend, on a flat stretch near our camp on a flattish area, I stayed in my skis while my bud de-skied and walked.

[sb]

Looks good, how do you like the straight across pockets as opposed to a 1/4 moon pockets ala Fischer?

Seems like the straight pocket gives max grip for smaller/shorter kick zone.

[GeezerSteve]

I surmise you are talking about Fischer's S-bound negative base (which, I believe, Fischer has replaced with a new positive base). I've got a few days on the Fischer negative "1/4 moon" base (apt description, BTW). But it's difficult for me to compare because the skis are very different and my DIY base is so much shorter.

I was able to mill something similar to, but not the same as, the old Fischer negative base. The grip of the straight step seemed to give a wee bit better grip, but only marginally so, and that might have been specific to the snow conditions (corn and dirty corn on my test days). Downhill performance and sideslipping seemed the same. (I milled the crescent and the straight step on a pair of old test skis, switched feet, etc.) Note that my straight step has a radius end, the result of using the end mill, and I think that helps with sideslipping. (As you know, straight step waxless patterns on XC skis w/o metal edges are cut all the way to the edge.) I tried several end mills -- including 1/2" and 3/4" HSS -- and got the best cut with the indexable ones with my sharpest (non-ferrous finish) carbide insert. 1" is my smallest indexable mill. Different p-tex mill seems to require different milling speeds. I got some melting on a shit p-tex base on one of my test skis. I slowed it down. Trab uses relatively hard p-tex. The Trab bases were scratched and gouged from spring touring, hence the less-than-clean look in the pics.

ETA: I'm a big fan of Fischer's Crown base on double-cambered XC skis of sufficient stiffness. (I have a pair of super stiff 58kg rated Superlight Crowns and RCS Crowns.) But I think the Crown Base would suck when turning downhill on an alpine flex ski.

ETA2:

Cool. How deep did you make the cuts. . . .

I did not measure depth. Shallow enough so that I left ample p-tex on the base. I flattened the camber and held the ski at 10 degrees to the mill. I tried more and less angle with some test skis, and 10 degrees seemed to work best, although that might vary with the profile of the end mill cutting surface.

[Meathelmet]

Cool shit. Thanks for protoing. Just to clarify, you mean by "positive base" that the actual ptex on the grip part comes "above" the zero line, like above edges? I am slow.

Had some old "proto mil-spec" Karhus at some point (tundra skis, like 225cm/70mm) that had some rows of dimples and some of the the long grooves you had as well made.
Worked well, relatively silent ,as it didnt have the who-whoo sound on harder snow than the later gen. Never seen that paricular "design" after that. Wonder what that was about..
The old/present Karhu mil skis had the tendency of being loudish..

Just to make sure, do the newer Voile BCs have a positive base as well, as you said, the base structure being above the edges? or does it have different design?


Edit : Corrections for spelling etc..

[GeezerSteve]

Edited this post after seeing Hohes post below: The industry has used the terms "negative" and "positive" to distinguished milled bases vs. molded bases with protruding ridges or scales. I heard the terms back in the late 1970s or early 1980s when I worked in shops that sold XC skis, including Trak, who boasted about its positive base. Positive base does not necessarily protrude above the bases; IMO that would be a bad design, i.e., railed skis.

No whizzing sound with this DIY fix. I'm deaf in one ear, so I asked my buds to confirm : )

Interesting note re those Karhus.

[coldfeet]

Thanks, you did mention the pattern length in the first post. I will consider adding "learning to read for comprehension" to my list of summer DIY projects.

Some or all of the Fischer negative patterns (before the recent change) were milled into the base - on my Outtabounds, you can see the machining marks. On ttips it is said that a sintered base has to be machined, so must be negative, while a positive base can be molded into extruded base material. The Outtabounds glide pretty decently I think, but they are a double camber ski with all that implies.

I'd like to try the machining approach, but would need to upgrade rotary tool and cutting bit.

Even just a little bit of waxless-pattern kick can make going places on flat and rolling terrain much more enjoyable. Kick wax might serve as well if the snow conditions were predictable enough, but they aren't here.

[neck beard]

I have had good times on my patterned Vectors. And noted the reduced suction on certain wet types of snow - sometimes I think they go faster! Can't ski them backwards for shit though. I can climb 15 degrees in soft spring all day. Not expecting good ascent performance in winter, but wont use them anyway. The Vector has a great shape as well.

Looking at Big Steve's comments above: my Vectors do not have a positive pattern. No part of the scales sit higher than the edges.

[GeezerSteve]

I might pick up a couple pairs of Vector BCs for me and the babe. Or will there be a Charger BC?

Okay, gotcha. I didn't read Meathelmet's post closely enough. The Vector BC looks to have a "positive base" as the XC industry defines it, i.e., the pattern is comprised of protruding ridges or scales. But sounds like the high point of the scales is flush with the base, i.e., Voile designed it right. That's good.

[AlpiNord]

Nice Steve. I imagine milling straight is much easier than trying to mimic a turning crown. Why do you think the crown would suck on down hilling?

[GeezerSteve]

Terry, I said that based on my experience on softish Fischer Crown XC skis, which sometimes tend to grab when turning on downhills. But I acknowledge that comparing XC flex skis, even soft ones, vs. alpine flex skis is apples vs. oranges. I'd like to get a couple strips of Crown base for experimentation.

Actually, I was able to mill and tested a "turning crown" similar to the S-Bound. This one seemed to grip about the same and seemed a bit better on the downhills.

ETA: The base came in handy last night at a few spots on our Silver Peak solstice tour.

[GeezerSteve]

8 touring days on these bases. I am declaring them a 100% success for spring tours. Will likely mill them on my 4 y.o. grunge APs for mid-winter tours next season.

They came in really handy on my skin across Pea Soup Lake on Saturday:

[neck beard]

Nice and fast, huh. Good stuff.

[splat]

I believe their was a thread here or somewhere I read about a DIY project with a router used to make the crowns. I'd imagine there's a pattern that could be incorporated into the milling that would allow equal up and down performance without sacrificing too much of either. Be cool to see some computer simulations.